Plasma has long been employed to process substrates (e. g., wafers or flat panels) to form electronic products (e.g., integrated circuits or flat panel displays). Semiconductor wafers are typically placed in an etch chamber with a photoresist mask layer to direct the etch of the underlying materials. The etching process removes the underlying materials not covered by the photoresist. The etch process may also remove material from the surfaces of parts within the plasma chamber. Over time, the parts inside the processing chamber may accumulate particulate matter and/or etch residues, which may alter the etch performance. For this reason, in addition to the need to replace consumable parts, there is also a need to perform wet clean operations (i.e., of the inside surfaces of chambers), periodically.
After a wet clean, the chamber must be reconditioned through various steps/processes (i.e., processed for wet clean recovery) before the chamber is allowed to proceed with production wafer processing. As a result, wet clean recovery is problematical. It is also difficult to match tools and getting more difficult. Tool matching is not just a matter of matching etch rate monitors but also profiles, uniformity of profiles, CDs, defects, etc. As a result, wet cleans take a long time even when executed well with lots of idle time awaiting metrology. Energy consumption is wasted during this time. Fabrication production time is also lost.
Part of the wet clean recovery procedure involves seasoning the chamber. This process attempts to produce surface conditions that mimic a steady state. When steady state is achieved, the solution tends to be brittle, i.e. it is not always universal from process to process or chamber to chamber. This requires expensive re-development procedures. Perhaps even worse, the seasoning itself can be a significant fraction of the total tool utilization, e.g. seasoning for 40 hours while the process only runs for 150-250 hours. Obviously, this is a productivity hit, not to mention again wasted energy consumption, cost of seasoning wafers, and high cost of consumables as they wear just to season them.
Waferless auto cleans (WACs) and pre-coats suffer from similar challenges. Systems are sometimes over-cleaned and over-pre-coated to enable mixed runs, stable operation, low defects, low metal contamination. The optimization of these procedures is necessarily done late in the development cycle, as it is too complicated to optimize them as recipes and wafer stacks are in flux.
It is in this context that embodiments arise.